1. Field of the Invention
The present invention relates to a monitor and a monitor system for monitoring overheating of the materials constituting the interior of a generator and the purity of gas in the interior of the generator.
2. Description of the Related Art
Since generators supply electric power which is important in a community, it is essential to prevent occurrence of accidents in them. For this purpose, there have been used apparatuses for monitoring the gas in generators and detecting occurrence of overheating by which the generators fail.
There have been proposed heretofore monitors for monitoring overheating in the interior of a generator in operation by xe2x80x9cImmediate Detection of Overheating in Gas-Cooled Electrical Machines (C. C. Carson et al., IEEE Conference Paper, 71C, p154 (1971)), xe2x80x9cThe Ion Chamber Detector as a Monitor of Thermally Produced Particlesxe2x80x9d (G. F. Skala, J. de Recherches Atmospherique, April-September, p189 (1966)), and U.S. Pat. Nos. 3,427,880, 3,573,460, and 3,972,225.
These conventional monitors are roughly divided into a monitor unit and a unit for confirming overheating by supporting the monitor, and the monitor is further divided into two devices using different measuring principles.
The conventional monitors will successively be described below.
FIG. 8 is a view showing a basic arrangement of a conventional monitor described in, for example, xe2x80x9cImmediate Detection of Overheating in Gas-cooled Electrical Machinesxe2x80x9d (C. C. Carson et al., IEEE Conference Paper, 71C, P154(1971)).
In FIG. 8, the conventional monitor 1 includes a main body vessel 2 having a pipe 3 connected thereto for introducing the cooling gas in the interior of a generator (not shown) into the vessel 2, an xcex1 ray source 4 for ionizing the cooling gas introduced into the main body vessel 2, a pair of electrodes 6 and 7 disposed in the vicinity of the gas outlet 5 of the main body vessel 2, an ammeter 8 for measuring the current flowing between the pair of electrodes 6 and 7, and a power supply 9 for imposing a voltage between the pair of electrodes 6 and 7.
Thorium is used as the xcex1 ray source 4. Further, hydrogen gas is used as the cooling gas.
Note that, while not shown, the current value measured with the ammeter 8 can be recorded on a recording sheet and the like.
Next, operation of the monitor 1 arranged as above will be described.
First, the monitor 1 is connected such that hydrogen gas as the cooling gas of the generator is introduced into the main body vessel 2 through the pipe 3 and the hydrogen gas discharged from the gas outlet 5 is returned into the interior of the generator.
Then, the cooling hydrogen gas in the interior of the generator is partly introduced into the main body vessel 2 through the pipe 3. The hydrogen gas introduced into the main body vessel 2 is ionized by an xcex1 ray irradiated from the xcex1 ray source 4. At that time, hydrogen is ionized, and ion pairs, that is, hydrogen ions having a positive charge and hydrogen ions having a negative charge are created. Then, the ionized hydrogen is partly attracted by and reaches the electrode 7, a current is generated between the electrode 7 and the main body vessel 2 (electrode 6), and the remaining hydrogen is discharged from the gas outlet 5, passing between the electrodes 6 and 7. The hydrogen gas discharged from the gas outlet 5 is returned in the interior of the generator.
When only hydrogen molecules exist in the cooling gas introduced into the main body vessel 2, the ionized hydrogen easily reaches the electrode 7 and a large ion current is observed by the ammeter 8 because the mass of the hydrogen molecules is very small.
In contrast, when small particles exist in the cooling gas in the interior of the generator, the number of hydrogen ions which reach the electrode 7 is reduced because the hydrogen ion pairs created in the main body vessel 2 bond to the small particles again and lose their charge. Further, while the small particles are ionized at the same time in the main body vessel 2, they do not almost reach the electrode 7 because it is difficult for the mass of the small particles to largely move. In short, when small particles exits in the cooling gas, the number of ions which reach the electrode 7 is reduced and current measured with the ammeter 8 is decreased.
Reduction of a current value caused by existence of small particles depends on Formula 1 as described in xe2x80x9cThe Ion Chamber Detector as a Monitor of Thermally Produced Particles (G. F. Skala, J. de Recherches Atmospherique, April-September, p189 (1966)).
xe2x88x92xcex94I=Qe(1xe2x88x92Fc)rZ/2xcex1xe2x80x83xe2x80x83(Formula 1)
where, xe2x88x92xcex94I is the reduction of a current value, Q is the flow rate of hydrogen gas, e is the elementary charge, Fc is the ratio of ionized small particles, r is the diameter of small particles, Z is the concentration of small particles in hydrogen gas, and xcex1 shows a rebonding constant of ions.
In (Formula 1), since Q, e, Fc and a are constants, when a small particle having a large product of r (diameter) and Z (concentration) exists, a current value measured with the ammeter 8 is reduced by xe2x88x92xcex94I as compared with a case in which the small particle does not exist.
Then, the small particles which can be detected with the conventional monitor 1 are specifically small particles having a diameter of 0.001 xcexcm to 0.1 xcexcm.
Next, the steps by which the conventional monitor 1 detects overheating in the interior of the generator will be described.
First, the value of a current flowing between the pair of electrodes 6 and 7 is measured with the ammeter 8 in the ordinary operating state of the generator in which overheating is not caused at all in the interior thereof, and the current value is recorded as a current level when the generator operates normally. Usually, the current value is measured successively at all times and recorded on a recording sheet and the like.
When a current value being monitored is lowered at a certain time, it is determined that small particles exist based on the principle shown by the above-mentioned Formula 1. In contrast, it is known that the materials in the interior of the generator generate small particles at the beginning of overheating. Therefore, when it is detected that a current is reduced by a value larger than a certain amount, it is determined that overheating is caused in the interior of the generator and an alarm is issued.
As described above, the conventional monitor 1 is a device for detecting the existence of small particles by the reduction of an ion current and has an object monitoring overheating of the generator by the detection of the small particles. Then, the conventional monitor 1 has only a function for detecting small particles and does not have a function for specifying the materials constituting detected small particles.
Further, the conventional monitor described in U.S. Pat. No. 3,427,880 is a device for detecting the existence of small particles by generating vapor droplets including small particles in cooling gas as nuclei and optically measuring the number of droplets and has an object for monitoring overheating of a generator by the detection of the small particles. Then, the conventional monitor also has only a function for detecting small particles and does not have a function for specifying the materials constituting detected small particles.
As described above, it is difficult for the conventional monitor 1 to specify whether detected small particles are generated by overheating or generated by friction and the like other than the overheating. Thus, a monitor used for determining whether the material in the interior of a generator is overheated or not is proposed in U.S. Pat. No. 3,972,255, and the like.
FIG. 9 is a view showing a basic arrangement of the conventional monitor described in, for example, U.S. Pat. No. 3,972,225.
In FIG. 9, the conventional monitor 10 includes a monitor unit 1 having a function for detecting whether small particles exist in the cooling gas of a generator 11 or not and a collection unit 12 having a function for collecting small particles. Then, the pipe 3 of the monitor 1 is connected to a pipe 14 through an open/close valve 17 and the gas outlet 5 of the monitor 1 is connected to the generator 11. Further, the pipe 15 of the collection unit 12 is connected to the pipe 14 through an open/close valve 18 and the gas outlet 16 of the collection unit 12 is connected to the generator 11.
Next, operation of the monitor 10 arranged as above will be described.
First, the open/close valve 17 is opened and the open/close valve 18 is closed. Then, the cooling gas in the generator 11 is partly introduced into the monitor 1 through the pipes 14 and 3 and returned into the generator 11 through the gas outlet 5. At that time, the monitor 1 monitors whether small particles exist in the cooling gas based on the magnitude of an ion current as described above. If the ion current is lower than the level of a threshold value, it is determined that small particles of a predetermined concentration exist and an alarm signal is output. When the alarm signal is output, the open/close valve 17 is opened after it is delayed a predetermined period of time by a delay relay 19 and introduction of cooling gas into the monitor 1 is stopped. Further, the alarm signal and an output from the delay relay 19 are supplied to a signal regulator 13 and the open/close valve 18 is opened in response to a signal output from the signal regulator 13. With this operation, the cooling gas is introduced into the collection unit 12 through the pipes 14 and 15 and thereafter returned to the generator 11 from the gas output 16. Then, small particles in the cooling gas are collected in the collection unit 12.
After a predetermined amount of the cooling gas is introduced as described above, the collection unit 12 is removed and the collected small particles are analyzed with another analyzer. Note that, in analysis, a gas chromatograph, mass spectrograph, infrared spectrograph and the like are ordinarily used independently or in combination. When the collected small particles are not metals and inorganic substances and are certain types of organic substances as the result of analysis, it is determined that overheating is caused in the interior of the generator 11.
Further, there is proposed by xe2x80x9cImplementation of Pyrolysate Analysis of Materials Employing Tagging Compounds to Locate an Overheated Area in a Generatorxe2x80x9d (S. C. Barton et al., IEEE Trans., PAS-100, 4983 (1981)) a method of previously applying a paint, from which small particles are liable to be generated, to the materials constituting the interior of a generator, collecting small particles by a conventional device similar to the monitor 10 and identifying the small particles with a gas chromatograph for the purpose of determining overheating of the generator at an earlier stage and specifying which portions in the interior of the generator are overheated.
Further, there is known a conventional example of an oil collection unit mounted on an oil-filled transformer. In the conventional example, after at least a predetermined amount of oil is collected by the oil collection unit, the collection unit is removed and the collected oil is analyzed separately with a gas chromatograph and the like.
The conventional device similar to the conventional monitor 10 is a device for collecting small particles in cooling gas and used to determine overheating the materials constituting the interior of a generator through analysis of collected materials.
The conventional monitor 1 has only the function for detecting small particles generated in a generator, and even if small particles are detected, it is difficult for the monitor 1 to find what types of materials the small particles are. That is, it is impossible for the conventional monitor 1 to make it apparent whether the small particles are organic components generated by overheating of the materials constituting the interior of a generator or mists of lubrication oil which have no relation with overheating. Thus, there is a problem in the conventional monitor 1 that even if the monitor 1 detects small particles and issues an alarm, there is a possibility that the alarm is issued by a cause such as lubrication oil and the like other than overheating and thus it cannot be instantly determined that overheating has been generated.
Further, the conventional monitor 10 making use of the collection unit 12 can analyze what materials small particles are and can assume that the small particles are generated by a constituting material. In the conventional monitor 10, however, since the gas in a generator must be caused to pass through the collection unit 12 once and then analyzed separately by removing the collection unit 12, there is a problem that a long time is necessary until overheating is determined. That is, since overheating of a generator cannot be determined at an early stage, there is a danger that an accident is caused thereby.
When a generator is overheated, it is preferable to specify an overheated portion at an early stage because it is necessary to repair an overheated portion instantly by stopping the generator. Since the conventional monitor 1 cannot specify a source from which small particles are generated, it is impossible for the monitor 1 to specify a portion where small particles are generated. Thus, there arises a problem in the conventional monitor 1 that even if overheating can be detected, a long time is necessary to restore a generator.
Further, when a special paint is applied to the interior of a generator and the conventional monitor 10 is used, there is a possibility to specify an overheated portion. When the conventional monitor 10 is used, however, since a long time is necessary to determine overheating as described above, there is a problem that an accident may be caused while the overheating is being determined and that this method is effective only to a generator the interior of which is previously painted. In general, since previous application of the paint has a problem that it is expensive and time-consuming, it cannot be said that this method is widely used in generators. Generators are scarcely painted, for example, in Japan. Accordingly, almost all the generators installed in Japan are not provided with devices capable of specifying a portion where overheating is caused.
An object of the present invention, which was made to solve the above problems, is to provide a generator interior cooling gas monitor and monitor system capable of giving determination in a short time, when overheating is caused in the interior of an existing generator, by detecting the overheating without the need of a separate analyzing method in the state in which the monitor and monitor system are connected to the generator. The term xe2x80x9cdecisionxe2x80x9d used here means to decide presence or absence of overheating and a degree of overheating when it is present by discriminating the occurrence of overheating in the materials constituting the interior of the generator from generation of mists from other materials such as, for example, lubrication oil.
Another object of the present invention is to provide a generator interior cooling gas monitor and monitor system capable of identifying a material constituting the interior of a generator or a portion of the generator from which overheating is caused in the state in which the monitor and monitor system are connected to the generator without previously applying a special paint to the interior of the generator and without using a separate analyzing method.
In order to achieve the above object, according to one aspect of the present invention, there is provided a generator interior cooling gas monitor which includes a cooling gas introduction pipe for introducing the cooling gas in the interior of a generator, a mass spectrograph connected to the cooling gas introduction pipe for separating the substances in the cooling gas introduced through the cooling gas introduction pipe in each mass of the substances and detecting them, and a computer for subjecting the data detected by the mass spectrograph to arithmetic operation and displaying the result of the arithmetic operation.
According to another aspect of the present invention, there is provided a generator interior cooling gas monitor system in which a plurality of sets of generator interior cooling gas monitors, each of which includes a cooling gas introduction pipe for introducing the cooling gas in the interior of a generator, a mass spectrograph connected to the cooling gas introduction pipe for separating the substances in the cooling gas introduced through the cooling gas introduction pipe in each mass of the substances and detecting them, and a computer for subjecting the data detected by the mass spectrograph to arithmetic operation and displaying the result of the arithmetic operation, are connected to each other through a computer network, and any of the monitors can perform monitoring and determination referring to the data of the monitors other than it.
According to still another aspect of the present invention, there is provided a generator interior cooling gas monitor system in which a generator interior cooling gas monitor, which includes a cooling gas introduction pipe for introducing the cooling gas in the interior of a generator, a mass spectrograph connected to the cooling gas introduction pipe for separating the substances in the cooling gas introduced through the cooling gas introduction pipe in each mass of the substances and detecting them, and a computer for subjecting the data detected by the mass spectrograph to arithmetic operation and displaying the result of the arithmetic operation, is connected to another monitor through a computer network so that the above monitor can perform monitoring and determination referring to the data of the another monitor.